1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a method for manufacturing a fluorescent powder substrate and a liquid crystal module using the fluorescent powder substrate.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal panel and a backlight module. The operation principle of the liquid crystal panel is that liquid crystal molecules are interposed between two parallel glass substrates and a plurality of vertical and horizontal fine electrical wires is arranged between the two glass substrates, whereby the liquid crystal molecules are controlled to change direction by application of electricity in order to refract light emitting from the backlight module to generate images. Since the liquid crystal panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of an LCD. The backlight module can be classified as two types, namely side-edge backlight module and direct backlight module, according to the position where light gets incident. The direct backlight module arranges a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED) at the back side of the liquid crystal panel to form a planar light source that directly provides lighting to the liquid crystal panel. The side-edge backlight module arranges a backlight source of LED light bar at an edge of a backplane to be located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face of the light guide plate and is projected out through a light exit face after being reflected and diffused to thereby form, after transmitting through a set of optic films, a planar light source for the liquid crystal panel.
The LED light bar comprises a printed circuit board (PCB) and LED lamps mounted to and electrically connected to the PCB. An LED lamp is often composed of a blue LED chip coated with YAG fluorescent powder (B+Y Powders) or a blue LED chip coated with RB (Red and Green) powders (B+RG Powders) in order to emit white light. The fluorescent powder is often mixed with epoxy resin and silica and is then packaged on the LED chip with a dispenser. In such a structure, the LED chip and the epoxy resin and the silica are set in tight engagement with each other, whereby heat dissipation from the LED chip is inefficient. This sets the LED chip long in a high temperature condition. However, epoxy resin is poor in resisting high temperature and being long set in a high temperature condition will lead to turning yellowish and reducing light emission performance. Further, being kept long in a high temperature condition may easily cause color fading and eventually results in shortened lifespan of the LED lamp and increase of cost.